1. FIELD OF THE INVENTION
This invention relates to nuclear reactor systems and, more particularly to pressurized water nuclear power reactor systems in which the heat exchanger is attached to a pressure vessel containing the core and which can be selectively disassembled.
2. DESCRIPTION OF THE PRIOR ART
Proposals have been advanced through the years to attached a pressure vessel containing a nuclear reactor core and associated pressurized water to a secondary coolant heat exchanger section to form a system capable of supplying heat energy for power generation or other purposes. A number of significant benefits are attainable through this structural configuration, especially if it is applied to shipboard and to land based electric power process energy uses.
One particular prior art reactor system of this nature has a heat exchanger in which the tubes are bent through 180.degree. to produce a "U" shape. This specific heat exchanger design requires the ends of the bent tubes to be secured in a tube sheet that is extremely thick, unwieldy and difficult to manufacture.
This "U" tube heat exchanger, moreover, is positioned directly above the reactor core. In these circumstances, this configuration of heat exchanger tends to require unorthodox control rod drive systems and undesirable coolant circulating pump arrangements.
In this respect, the operation of the nuclear reactor is regulated by means of control rods which are inserted into and withdrawn from the reactor core in response to power demands. Control rod drive motors, mounted on the exterior surface of the cylindrical portion of the pressure vessel transmit power through a 90.degree. angle to drive these control rods in desired directions relative to the reactor core. Not only is this a mechanically awkward arrangement, but it also increases the vulnerability of the control rod drive mechanism to potential malfunctions.
The coolant circulating pumps are mounted externally on "stalks" which are difficult to manufacture. Furthermore, these stalks, which consist of concentric piping of relatively large diameter, tend to compromise the intrinsic safety of an integrally arranged pressurized water reactor system due to the possibility (though remote) of their failure.
Clearly, there is a need for an integral reactor and heat exchanger system that reduces the thickness of the tube sheet and makes the reactor core more readily accessible for inspection and refueling, in addition to providing a less complicated, and hence more reliable control rod drive mechanism.
The above complications also tend to limit the thermal power range of this system to levels below 100 megawatts. By contrast, it is the intent of this invention to provide an integral pressured water reactor system capable of power levels to at least 1500 thermal megawatts.